[PATCH] Include explicit instantiations of iostream inserters and extractors in string.cpp.

[Peter Collingbourne]

On Sat, Sep 21, 2013 at 07:09:48PM -0400, Howard Hinnant wrote:
> On Sep 21, 2013, at 6:59 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
> 
> > On Sat, Sep 21, 2013 at 05:23:18PM -0400, Howard Hinnant wrote:
> >> Can you show a conforming example that demonstrates this problem?  My thinking has been that there is no way to use these functions in a conforming manner wtih including <{i,o}stream>.
> > 
> > This is what I had in mind:
> > 
> > TU1:
> > ========================================================================
> > #include <iosfwd>
> > #include <string>
> > 
> > void f(std::ostream &os, const std::string &s) {
> >  os << s;
> > }
> > ========================================================================
> > 
> > TU2:
> > ========================================================================
> > #include <iostream>
> > #include <string>
> > 
> > using namespace std;
> > 
> > void f(ostream &os, const string &s);
> > 
> > int main() {
> >  f(cout, "hello world");
> > }
> > ========================================================================
> > 
> > I believe this is conforming, but I may be mistaken.
> > 
> > Thanks,
> > -- 
> > Peter
> 
> I believe 17.6.2.2 [using.headers]/p3 makes TU1 non-conforming:
> 
> > A translation unit shall include a header only outside of any external declaration or definition, and shall include the header lexically before the first reference in that translation unit to any of the entities declared in that header. No diagnostic is required.
> 
> #include <ostream> is required in TU1.

Would #include <iosfwd> not satisfy this requirement as for the
reference to std::ostream?  I haven't found anything that would
prevent the forward declarations in <iosfwd> from being considered
declarations for the purpose of [using.headers]p3.

Thanks,
-- 
Peter